I own a 1993 Toyota 22-RE standard cab 2wd pickup.

ALL of this started occurring after the water pump and alternator drive belt took a dump on me.. I drove it home about 2-5 minutes made it there just fine. Have put about 3-5k miles on it since then.. truck runs great.

The temperature gauge 90% of the time goes ALL the way over to max HOT as soon as I start it up... cold start or hot start. Sometimes like maybe when its raining... the temperature gauge will function like it should but only bound to go crazy again. Rarely it will work normally on a cold startup but usually ends up going all the way to HOT side after a few minutes of driving. When I unplug the connector at the sensor(cold start)... the gauge will sometimes go to the normal halfway mark where it should be @ operating temperature.. sometimes it will stay on max HOT. It has a mind of its own. I can tell its not overheating by feeling the block/head/valve cover by hand. Radiator hoses feel fine everything feels fine. It takes the truck normal time to warm up and put out good heat. I've replaced the temp. sensor, have searched for shorts to ground and power a little but not a lot. I read somewhere on a forum that had the similar problem, they took the instrument cluster out and on the back near the temp. gauge there are 3 or so little black screws that loosen overtime and cause random paths to ground etc?, tightening these screws and applying loctite where they wont back out again fixed the problem.. Supposedly worked for a few people. My dash is cracked to ˟˟˟˟ and have a dash cover on it.. would like not to take it off if possible.

Very very rarely it will cause me a hard-start during a cold start.... the ECT is one of the more important sensors for a cold initial start up and I'am surprised it doesn't actually cause me hard-starts much more often than what it does.. this gauge is driving me nuts and I wonder if PCM is commanding excess fuel dumping into cylinders because it thinks its always overheating... my gas mileage is pretty damn good already

Any tips or similar experience you wish to share would be appreciated. thanks

 

I had to replace the sending unit in mine. It would always shoot up to max temp but after that fix it works fineeeee maybe bad sending unit

 

I had a similar issue and just cleaned the sensor, but see you changed yours, maybe it is a bad one.

Have you tried burping your system since you changed water pumps? Possibly got air in the system. Park on a steep incline or raise the front end up quite a bit and pull the radiator cap off. Let the thermostat cycle a few times and see if any air comes out.